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Diffstat (limited to '.venv/lib/python3.12/site-packages/networkx/algorithms/minors/tests')
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diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/minors/tests/test_contraction.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/minors/tests/test_contraction.py new file mode 100644 index 00000000..22468867 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/minors/tests/test_contraction.py @@ -0,0 +1,446 @@ +"""Unit tests for the :mod:`networkx.algorithms.minors.contraction` module.""" + +import pytest + +import networkx as nx +from networkx.utils import arbitrary_element, edges_equal, nodes_equal + + +def test_quotient_graph_complete_multipartite(): + """Tests that the quotient graph of the complete *n*-partite graph + under the "same neighbors" node relation is the complete graph on *n* + nodes. + + """ + G = nx.complete_multipartite_graph(2, 3, 4) + # Two nodes are equivalent if they are not adjacent but have the same + # neighbor set. + + def same_neighbors(u, v): + return u not in G[v] and v not in G[u] and G[u] == G[v] + + expected = nx.complete_graph(3) + actual = nx.quotient_graph(G, same_neighbors) + # It won't take too long to run a graph isomorphism algorithm on such + # small graphs. + assert nx.is_isomorphic(expected, actual) + + +def test_quotient_graph_complete_bipartite(): + """Tests that the quotient graph of the complete bipartite graph under + the "same neighbors" node relation is `K_2`. + + """ + G = nx.complete_bipartite_graph(2, 3) + # Two nodes are equivalent if they are not adjacent but have the same + # neighbor set. + + def same_neighbors(u, v): + return u not in G[v] and v not in G[u] and G[u] == G[v] + + expected = nx.complete_graph(2) + actual = nx.quotient_graph(G, same_neighbors) + # It won't take too long to run a graph isomorphism algorithm on such + # small graphs. + assert nx.is_isomorphic(expected, actual) + + +def test_quotient_graph_edge_relation(): + """Tests for specifying an alternate edge relation for the quotient + graph. + + """ + G = nx.path_graph(5) + + def identity(u, v): + return u == v + + def same_parity(b, c): + return arbitrary_element(b) % 2 == arbitrary_element(c) % 2 + + actual = nx.quotient_graph(G, identity, same_parity) + expected = nx.Graph() + expected.add_edges_from([(0, 2), (0, 4), (2, 4)]) + expected.add_edge(1, 3) + assert nx.is_isomorphic(actual, expected) + + +def test_condensation_as_quotient(): + """This tests that the condensation of a graph can be viewed as the + quotient graph under the "in the same connected component" equivalence + relation. + + """ + # This example graph comes from the file `test_strongly_connected.py`. + G = nx.DiGraph() + G.add_edges_from( + [ + (1, 2), + (2, 3), + (2, 11), + (2, 12), + (3, 4), + (4, 3), + (4, 5), + (5, 6), + (6, 5), + (6, 7), + (7, 8), + (7, 9), + (7, 10), + (8, 9), + (9, 7), + (10, 6), + (11, 2), + (11, 4), + (11, 6), + (12, 6), + (12, 11), + ] + ) + scc = list(nx.strongly_connected_components(G)) + C = nx.condensation(G, scc) + component_of = C.graph["mapping"] + # Two nodes are equivalent if they are in the same connected component. + + def same_component(u, v): + return component_of[u] == component_of[v] + + Q = nx.quotient_graph(G, same_component) + assert nx.is_isomorphic(C, Q) + + +def test_path(): + G = nx.path_graph(6) + partition = [{0, 1}, {2, 3}, {4, 5}] + M = nx.quotient_graph(G, partition, relabel=True) + assert nodes_equal(M, [0, 1, 2]) + assert edges_equal(M.edges(), [(0, 1), (1, 2)]) + for n in M: + assert M.nodes[n]["nedges"] == 1 + assert M.nodes[n]["nnodes"] == 2 + assert M.nodes[n]["density"] == 1 + + +def test_path__partition_provided_as_dict_of_lists(): + G = nx.path_graph(6) + partition = {0: [0, 1], 2: [2, 3], 4: [4, 5]} + M = nx.quotient_graph(G, partition, relabel=True) + assert nodes_equal(M, [0, 1, 2]) + assert edges_equal(M.edges(), [(0, 1), (1, 2)]) + for n in M: + assert M.nodes[n]["nedges"] == 1 + assert M.nodes[n]["nnodes"] == 2 + assert M.nodes[n]["density"] == 1 + + +def test_path__partition_provided_as_dict_of_tuples(): + G = nx.path_graph(6) + partition = {0: (0, 1), 2: (2, 3), 4: (4, 5)} + M = nx.quotient_graph(G, partition, relabel=True) + assert nodes_equal(M, [0, 1, 2]) + assert edges_equal(M.edges(), [(0, 1), (1, 2)]) + for n in M: + assert M.nodes[n]["nedges"] == 1 + assert M.nodes[n]["nnodes"] == 2 + assert M.nodes[n]["density"] == 1 + + +def test_path__partition_provided_as_dict_of_sets(): + G = nx.path_graph(6) + partition = {0: {0, 1}, 2: {2, 3}, 4: {4, 5}} + M = nx.quotient_graph(G, partition, relabel=True) + assert nodes_equal(M, [0, 1, 2]) + assert edges_equal(M.edges(), [(0, 1), (1, 2)]) + for n in M: + assert M.nodes[n]["nedges"] == 1 + assert M.nodes[n]["nnodes"] == 2 + assert M.nodes[n]["density"] == 1 + + +def test_multigraph_path(): + G = nx.MultiGraph(nx.path_graph(6)) + partition = [{0, 1}, {2, 3}, {4, 5}] + M = nx.quotient_graph(G, partition, relabel=True) + assert nodes_equal(M, [0, 1, 2]) + assert edges_equal(M.edges(), [(0, 1), (1, 2)]) + for n in M: + assert M.nodes[n]["nedges"] == 1 + assert M.nodes[n]["nnodes"] == 2 + assert M.nodes[n]["density"] == 1 + + +def test_directed_path(): + G = nx.DiGraph() + nx.add_path(G, range(6)) + partition = [{0, 1}, {2, 3}, {4, 5}] + M = nx.quotient_graph(G, partition, relabel=True) + assert nodes_equal(M, [0, 1, 2]) + assert edges_equal(M.edges(), [(0, 1), (1, 2)]) + for n in M: + assert M.nodes[n]["nedges"] == 1 + assert M.nodes[n]["nnodes"] == 2 + assert M.nodes[n]["density"] == 0.5 + + +def test_directed_multigraph_path(): + G = nx.MultiDiGraph() + nx.add_path(G, range(6)) + partition = [{0, 1}, {2, 3}, {4, 5}] + M = nx.quotient_graph(G, partition, relabel=True) + assert nodes_equal(M, [0, 1, 2]) + assert edges_equal(M.edges(), [(0, 1), (1, 2)]) + for n in M: + assert M.nodes[n]["nedges"] == 1 + assert M.nodes[n]["nnodes"] == 2 + assert M.nodes[n]["density"] == 0.5 + + +def test_overlapping_blocks(): + with pytest.raises(nx.NetworkXException): + G = nx.path_graph(6) + partition = [{0, 1, 2}, {2, 3}, {4, 5}] + nx.quotient_graph(G, partition) + + +def test_weighted_path(): + G = nx.path_graph(6) + for i in range(5): + G[i][i + 1]["w"] = i + 1 + partition = [{0, 1}, {2, 3}, {4, 5}] + M = nx.quotient_graph(G, partition, weight="w", relabel=True) + assert nodes_equal(M, [0, 1, 2]) + assert edges_equal(M.edges(), [(0, 1), (1, 2)]) + assert M[0][1]["weight"] == 2 + assert M[1][2]["weight"] == 4 + for n in M: + assert M.nodes[n]["nedges"] == 1 + assert M.nodes[n]["nnodes"] == 2 + assert M.nodes[n]["density"] == 1 + + +def test_barbell(): + G = nx.barbell_graph(3, 0) + partition = [{0, 1, 2}, {3, 4, 5}] + M = nx.quotient_graph(G, partition, relabel=True) + assert nodes_equal(M, [0, 1]) + assert edges_equal(M.edges(), [(0, 1)]) + for n in M: + assert M.nodes[n]["nedges"] == 3 + assert M.nodes[n]["nnodes"] == 3 + assert M.nodes[n]["density"] == 1 + + +def test_barbell_plus(): + G = nx.barbell_graph(3, 0) + # Add an extra edge joining the bells. + G.add_edge(0, 5) + partition = [{0, 1, 2}, {3, 4, 5}] + M = nx.quotient_graph(G, partition, relabel=True) + assert nodes_equal(M, [0, 1]) + assert edges_equal(M.edges(), [(0, 1)]) + assert M[0][1]["weight"] == 2 + for n in M: + assert M.nodes[n]["nedges"] == 3 + assert M.nodes[n]["nnodes"] == 3 + assert M.nodes[n]["density"] == 1 + + +def test_blockmodel(): + G = nx.path_graph(6) + partition = [[0, 1], [2, 3], [4, 5]] + M = nx.quotient_graph(G, partition, relabel=True) + assert nodes_equal(M.nodes(), [0, 1, 2]) + assert edges_equal(M.edges(), [(0, 1), (1, 2)]) + for n in M.nodes(): + assert M.nodes[n]["nedges"] == 1 + assert M.nodes[n]["nnodes"] == 2 + assert M.nodes[n]["density"] == 1.0 + + +def test_multigraph_blockmodel(): + G = nx.MultiGraph(nx.path_graph(6)) + partition = [[0, 1], [2, 3], [4, 5]] + M = nx.quotient_graph(G, partition, create_using=nx.MultiGraph(), relabel=True) + assert nodes_equal(M.nodes(), [0, 1, 2]) + assert edges_equal(M.edges(), [(0, 1), (1, 2)]) + for n in M.nodes(): + assert M.nodes[n]["nedges"] == 1 + assert M.nodes[n]["nnodes"] == 2 + assert M.nodes[n]["density"] == 1.0 + + +def test_quotient_graph_incomplete_partition(): + G = nx.path_graph(6) + partition = [] + H = nx.quotient_graph(G, partition, relabel=True) + assert nodes_equal(H.nodes(), []) + assert edges_equal(H.edges(), []) + + partition = [[0, 1], [2, 3], [5]] + H = nx.quotient_graph(G, partition, relabel=True) + assert nodes_equal(H.nodes(), [0, 1, 2]) + assert edges_equal(H.edges(), [(0, 1)]) + + +def test_undirected_node_contraction(): + """Tests for node contraction in an undirected graph.""" + G = nx.cycle_graph(4) + actual = nx.contracted_nodes(G, 0, 1) + expected = nx.cycle_graph(3) + expected.add_edge(0, 0) + assert nx.is_isomorphic(actual, expected) + + +def test_directed_node_contraction(): + """Tests for node contraction in a directed graph.""" + G = nx.DiGraph(nx.cycle_graph(4)) + actual = nx.contracted_nodes(G, 0, 1) + expected = nx.DiGraph(nx.cycle_graph(3)) + expected.add_edge(0, 0) + expected.add_edge(0, 0) + assert nx.is_isomorphic(actual, expected) + + +def test_undirected_node_contraction_no_copy(): + """Tests for node contraction in an undirected graph + by making changes in place.""" + G = nx.cycle_graph(4) + actual = nx.contracted_nodes(G, 0, 1, copy=False) + expected = nx.cycle_graph(3) + expected.add_edge(0, 0) + assert nx.is_isomorphic(actual, G) + assert nx.is_isomorphic(actual, expected) + + +def test_directed_node_contraction_no_copy(): + """Tests for node contraction in a directed graph + by making changes in place.""" + G = nx.DiGraph(nx.cycle_graph(4)) + actual = nx.contracted_nodes(G, 0, 1, copy=False) + expected = nx.DiGraph(nx.cycle_graph(3)) + expected.add_edge(0, 0) + expected.add_edge(0, 0) + assert nx.is_isomorphic(actual, G) + assert nx.is_isomorphic(actual, expected) + + +def test_create_multigraph(): + """Tests that using a MultiGraph creates multiple edges.""" + G = nx.path_graph(3, create_using=nx.MultiGraph()) + G.add_edge(0, 1) + G.add_edge(0, 0) + G.add_edge(0, 2) + actual = nx.contracted_nodes(G, 0, 2) + expected = nx.MultiGraph() + expected.add_edge(0, 1) + expected.add_edge(0, 1) + expected.add_edge(0, 1) + expected.add_edge(0, 0) + expected.add_edge(0, 0) + assert edges_equal(actual.edges, expected.edges) + + +def test_multigraph_keys(): + """Tests that multiedge keys are reset in new graph.""" + G = nx.path_graph(3, create_using=nx.MultiGraph()) + G.add_edge(0, 1, 5) + G.add_edge(0, 0, 0) + G.add_edge(0, 2, 5) + actual = nx.contracted_nodes(G, 0, 2) + expected = nx.MultiGraph() + expected.add_edge(0, 1, 0) + expected.add_edge(0, 1, 5) + expected.add_edge(0, 1, 2) # keyed as 2 b/c 2 edges already in G + expected.add_edge(0, 0, 0) + expected.add_edge(0, 0, 1) # this comes from (0, 2, 5) + assert edges_equal(actual.edges, expected.edges) + + +def test_node_attributes(): + """Tests that node contraction preserves node attributes.""" + G = nx.cycle_graph(4) + # Add some data to the two nodes being contracted. + G.nodes[0]["foo"] = "bar" + G.nodes[1]["baz"] = "xyzzy" + actual = nx.contracted_nodes(G, 0, 1) + # We expect that contracting the nodes 0 and 1 in C_4 yields K_3, but + # with nodes labeled 0, 2, and 3, and with a -loop on 0. + expected = nx.complete_graph(3) + expected = nx.relabel_nodes(expected, {1: 2, 2: 3}) + expected.add_edge(0, 0) + cdict = {1: {"baz": "xyzzy"}} + expected.nodes[0].update({"foo": "bar", "contraction": cdict}) + assert nx.is_isomorphic(actual, expected) + assert actual.nodes == expected.nodes + + +def test_edge_attributes(): + """Tests that node contraction preserves edge attributes.""" + # Shape: src1 --> dest <-- src2 + G = nx.DiGraph([("src1", "dest"), ("src2", "dest")]) + G["src1"]["dest"]["value"] = "src1-->dest" + G["src2"]["dest"]["value"] = "src2-->dest" + H = nx.MultiDiGraph(G) + + G = nx.contracted_nodes(G, "src1", "src2") # New Shape: src1 --> dest + assert G.edges[("src1", "dest")]["value"] == "src1-->dest" + assert ( + G.edges[("src1", "dest")]["contraction"][("src2", "dest")]["value"] + == "src2-->dest" + ) + + H = nx.contracted_nodes(H, "src1", "src2") # New Shape: src1 -(x2)-> dest + assert len(H.edges(("src1", "dest"))) == 2 + + +def test_without_self_loops(): + """Tests for node contraction without preserving -loops.""" + G = nx.cycle_graph(4) + actual = nx.contracted_nodes(G, 0, 1, self_loops=False) + expected = nx.complete_graph(3) + assert nx.is_isomorphic(actual, expected) + + +def test_contract_loop_graph(): + """Tests for node contraction when nodes have loops.""" + G = nx.cycle_graph(4) + G.add_edge(0, 0) + actual = nx.contracted_nodes(G, 0, 1) + expected = nx.complete_graph([0, 2, 3]) + expected.add_edge(0, 0) + expected.add_edge(0, 0) + assert edges_equal(actual.edges, expected.edges) + actual = nx.contracted_nodes(G, 1, 0) + expected = nx.complete_graph([1, 2, 3]) + expected.add_edge(1, 1) + expected.add_edge(1, 1) + assert edges_equal(actual.edges, expected.edges) + + +def test_undirected_edge_contraction(): + """Tests for edge contraction in an undirected graph.""" + G = nx.cycle_graph(4) + actual = nx.contracted_edge(G, (0, 1)) + expected = nx.complete_graph(3) + expected.add_edge(0, 0) + assert nx.is_isomorphic(actual, expected) + + +def test_multigraph_edge_contraction(): + """Tests for edge contraction in a multigraph""" + G = nx.cycle_graph(4) + actual = nx.contracted_edge(G, (0, 1, 0)) + expected = nx.complete_graph(3) + expected.add_edge(0, 0) + assert nx.is_isomorphic(actual, expected) + + +def test_nonexistent_edge(): + """Tests that attempting to contract a nonexistent edge raises an + exception. + + """ + with pytest.raises(ValueError): + G = nx.cycle_graph(4) + nx.contracted_edge(G, (0, 2)) |